quiet, upscale neighborhood of Dallas, in this house on Colgate avenue, that a life changing drama was about to play out. What seemed like the strongest lead yet in finding the stolen baby. 49-year-old Sam miller, adopted under what he called unusual circumstances, a mirror image of one of the age progression drawings of what the baby would look like today. And the baby photos of the two, hard to tell them apart. We were there when he got the phone call that would resolve it all. From the government office in Chicago that had his original adoption papers, which 20/20 helped to get unsealed. I appreciate it. I would like to know who I am. Reporter: It was a 90 second phone call. Full of nervous anticipation. As miller learned what was found in the adoption files that that had been kept secret until this moment. My birth mother was -- Shiela -- Reporter: If true, that meant he had not been stolen, but give up for adoption legitimately. So you're not the stolen baby? No. They found my original birth certificate. Reporter: For Sam and his family, hugs and tears and disappointment. You okay? Yeah, I'll be fine. Reporter: And a new search for a family he needs to find as he faces a kidney transplant to keep him alive. I have a brand-new search. Thank you so much for flying down. Reporter: Of course. I appreciate it. Reporter: For us, it was back to Chicago and the discovery on the "20/20" tipline of what, amazingly, would turn out to be an even more intriguing lead about who the kidnapper might be. You know who stole this baby? Yes. Reporter: Who stole the baby? My mother. Reporter: Your mother stole the baby? Yes. Reporter: His name in Johnnie Harbaugh and what he told us about his mother may seem far-fetched, but it most definitely is not. It's a pretty serious charge that your mother kidnapped a baby. Right. But she was arrested a few times for suspicious of kidnapping babies. Reporter: His mother's name was Linda Taylor, a notorious figure in Chicago in the 1970s and '80s, dubbed America's welfare queen and vilified by president Ronald Reagan. Her name is Linda Taylor, the alleged Illinois legislative advisory committee on public assistance investigated, came up with 82 charges of welfare fraud, perjury and bigamy. Among other things they discovered 100 aliases and 50 false addresses. We began to look for her after our "20/20" tipline provided this clue. The baby was stolen by a lady known as the welfare queen. She had many, many schemes to get money and would have most likely sold the baby. Linda Taylor died 12 years ago but we found her son living in a Chicago suburb, prepared he said, to finally tell what he knows about his mother and the stolen baby. Did he have a name? He had a name, but we called him tiger. Reporter: Harbaugh said he was a teenager living in this house in Chicago, when he came home to discover a new baby. Was your mother capable of stealing a baby? My mother was capable of anything. Not only stealing a baby, but she could steal you. She wasust that kind of woman, you know. She done whatever it took for her to survive. Reporter: Harbaugh said his mother was a master of disguise, could pass as white or black, Puerto rican or hawaiian, in her schemes to collect fraudulent welfare payments, sometimes posing as a doctor or a nurse. She had a room with nothing but wigs and nurse dresses and shoes. Reporter: At the time that Paul Fronczak was stolen from the Michael Reese hospital the police put out a sketch. Yes. Reporter: Do you -- do you think that's your mother? Except for the nose. But she could do anything with her face or her hair. Reporter: In the 1970s, when Linda Taylor was put on trial for welfare fraud, she actually came under investigation for stealing the Fronczak baby. From one newspaper account, quote, "One of her ex-husbands told agents that miss Taylor appeared on day in the mid-1960s with a newborn baby although she had not been pregnant." That would not surprise me. Reporter: Isaiah gant was Linda Taylor's lawyer at the time and told "20/20" she never admitted anything but he wouldn't put it past her to snatch a baby. The woman was just a C chameleon. She could be anything. So I couldn't rule out the possibility that she could be involved in something like that. Reporter: Her son Johnnie says he was already in trouble with the law then, and never volunteered what he says he knew about the Fronczak baby, until he talked with us and a reporter for the online news site slate. I wasn't gonna go tell somebody, hey I know where this baby is, you know. You didn't do stuff like that back then. Reporter: Harbaugh says he came home from school one day, and the baby was gone, taken, he believes, by one of his mother's boyfriends to Tennessee. But you're sure about this. I'm positive. Reporter: Harbaugh said the man who took the baby worked at what was then the American rivet company. A former employee there confirmed to 20/20 the name Harbaugh gave us, and said the man, indeed, had moved to a small town in Tennessee. ? our "20/20" investigative team went to Tennessee, to the town of sevierville. But we could find no current record of the man who supposedly took the stolen baby here so many years ago. What would you say to the Fronczak parents, Mr. And Mrs. Fronczak that had their baby taken away, day and a half old? Back then I was young. You know, a baby, you know, and I seen so many of them. But I would -- I'm -- I mean, there's nothing I could say to 'em. I mean, I couldn't apologize enough for not turning her in. Reporter: Cold comfort for the Fronczak parents so many years later. Until tonight, Chester and Dora Fronczak declined to comment on the new investigation, but this week they sent their first public statement to "20/20" staying we wish Paul well in his search and we continue to cooperate in the FBI in our hope for answers. Next -- All of a sudden this name pops up. For the first time a family reunion 50 years in the Sprint's

This transcript has been automatically generated and may not be 100% accurate.

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